In order to start up a completely autotrophic nitrogen removal over nitrite (CANON) process

the continuous flow and sequencing batch modes were used in stages to operate the completely mixed flow reactor inoculated with nitrosation granular sludges. The variations of reactor performance

sludge morphology and activity

and the microbial community structure were investigated in details. Results showed that sequencing batch operation could promote the increases in both sludge concentration and reaction activity at high influent ammonium loading rate and high dissolved oxygen level

on basis of an appropriate nitrogen substrate ratio obtained in the initial continuous flow stage. Then a superior total nitrogen removal rate of 1.75 kg·(m3·d)-1 was achieved in the subsequent continuous flow mode. During the operation period

the compactness and settling property of granules were improved obviously. And Miseq high-throughput pyrosequencing analysis revealed that CANON granular sludge showed a relative higher microbial diversity. Corresponding to the specific nitrogen removal rate of 0.24 g·(g VSS·d)-1

the abundance ratio between aerobic and anaerobic ammonium oxidation bacteria was around 3 to 1

in terms of gene Nitrosomonas and Candidatus Kuenenia

respectively. In addition

few oligotrophic nitrite oxidation bacteria in the granules would not affect the efficiency of CANON process significantly.